Apparatus for producing more than one grade of malleable iron from a single high carbon charge thereof



Jan. 25, 1966 s THOMPSON 3,231,253

.E.. APPARATUS FOR PRODUCING MORE THAN ONE GRADE OF MALLEABLE IGH CARBONCHARGE THEREOF IRON FROM A SINGLE H Filed Feb. 28, 1963 finals/P7 E. 5.THOMPSON B @wzg y ATTORNEYS United States Patent Office APPARATUS FORPRODUCENG MQRE THAN @NE GRADE F MALLEABLE IRQN FRUM A SINGLE HIGH CARBONQHARGE THEREOF Robert E. S. Thompson, Guiiford, Conn, assignor toMalleable Iron Fittings Company, Branford, Conn, a corporation ofConnecticut Filed Feb. 23, 1963, Ser. No. 261,605 9 Claims. (Cl.266--13) This invention relates to malleable iron production and, moreparticularly, to an apparatus by means of which two or more differentgrades of refined iron can be produced from a single high-carbon melt.

The customary procedure in the foundry industry is to scheduleproduction of a number of different products requiring an iron with anarrow range of carbon content. The iron is melted in a shaft furnaceknown as a cupola. The cupola charge is adjusted to give the requiredanalysis except that the carbon content is higher than desired. The meltfrom the coupola furnace is subsequently transferred to a refiningfurnace where such adjustments in the carbon content as may be requiredare carried out to meet the particular carbon range desired. Thispractice requires that the products cast on each of several castinglines make use of iron having substantially the same composition.

In the malleable iron foundry industry, the problem of producing morethan one grade of iron from a single or tandem (duplex) melting unit,has long existed and has been considered insurmountable. The threemalleable grades covered by ASTM specifications, A197 and A47, differmainly in the carbon content of the iron poured to produce them. Thecarbon content of A47, grade 35 018, generally ranges from 2.15 to 2.40%that of A47, grade 32510, from 2.40 to 2.60%; and that of A197 from 2.70to 3.00%.

The mechanical test values of these three grades are:

The 35018 material is used in applications where strength and toughness,comparable to that of steel castings, is important. It is also generallyconsidered to be the most dependable material for heavy (thick) sectionapplications due to the decreased possibility of primary graphiteoccurrence.

The 32510 material has wide use in castings for the automotive industryand elsewhere, where a good average strong tough grade of malleable wellmeets all requirements.

The A197 grade is used mainly in the lighter section pipe, and otherfittings where its high fluidity well serves and where the sections areso light (thin) that there is little danger of the formation ofweakening primary graphite.

More recently, ductile iron has become a foundry product. Since itsproduction requires a different composition, from the standpoint ofcarbon and other elements, the possibility of its advantageousproduction, along with malleable, from one melting source, is manifest.

Similarly, where high strength or pearlitic gray iron is required, greatcontrol and economic advantage would accrue to its being produced fromthe same melting source as malleable.

Patented .Fan. 25, 1966 It would appear from the foregoing that anobvious solution would be to employ several hot-metal production unitseach of which would include both a cupola and a refining furnace thatcould be used for a certain grade of production; however, in mostinstances this is not the case because such a practice is mostuneconomical. The reason for this is that a single cupola and refiningfurnace assembly is generally entirely adequate to supply all thehot-metal requirements for the entire foundry production and it would,therefore, involve anunnecessary duplication of expense to equip afoundry with duplicate hotmetal production facilities for the solepurpose of having more than one grade of iron available at all times.

A much more practical solution to this problem would be, of course, toprovide a single hot-metal production facility capable of being used toproduce more than one grade of iron from a single melt along with theattendant processing procedures by which the melt could be altered tosuit varying production requirements. It has now been found inaccordance with the teaching of the instant invention that theaforementioned desirable ends can be accomplished insofar as theequipment is concerned through the simple, but unobvious, expedient ofcompartmentalizing the refining furnace and altering the connectionsbetween the single cupola furnace so that the output therefrom can bedivided and delivered to the several compartments of the refiningfurnace. From the process standpoint, a single high-carbon charge is fedto the cupola furnace, melted, and distributed to the severalcompartments of the refining furnace where the resulting fractionalportions are subjected to individual treatments designed to materiallyalter their composition. For example, one compartment of the refiningfurnace would contain iron of the same composition as the originalcharge to the cupola in all probability. Asecond compartment wouldlikely contain a medium-carbon composition produced by oxidation of theoriginal cupola melt to reduce the carbon content thereof with aprocess, the details of which will be more fully set forth presently.Many foundry operations will require only a two-compartment refiningfurnace because high and medium carbon melts will satisfy the majorityof their production needs and special alloys, low-carbon semi-steels andthe like could be made in one of the compartments whenever therequirements for high or medium carbon iron were not pressing; however,there would be nothing to prevent further compartmentalization of therefining furnace to accommodate simultaneous production of more than twogrades of iron and its alloys.

It is, therefore, the principal object of the present invention toprovide novel apparatus suitable for use in the simultaneous productionof more than one grade of malleable iron and alloys thereof.

A second object of the invention herein described is the provision of acompartmentalized refining furnace useful in combination with a singlecupola furnace to produce hotmetal batches of different composition froma single charge.

Another objective of the invention is to provide a refining furnaceespecially designed and adapted for use in carrying out substantialvariations in the composition of a melt including reduction of thecarbon-content and the addition of ferro-alloys.

Still another object is to provide a hot-metal production facility forfoundries that makes constantly available two or more different gradesof iron yet does not require duplication of cupola and refiningfurnaces.

Further objects of the invention herein disclosed are the provision ofapparatus for hot-metal production in a foundry that are versatile,inexpensive, easy to use, efiicient, economical to operate and readilyadaptable to existing facilities.

Other objects will be in part apparent and in part pointed outspecifically hereinafter in connection with the description of thedrawings that follows, and in which:

FIGURE 1 is a top plan view, somewhat schematic in character, showingthe hot-metal production facility of the present invention; and,

FIGURE 2 is a vertical longitudinal section showing thecompartmentalized refining furnace that forms a part of such a hot-metalproduction apparatus.

Referring now to the drawings for a detailed description of the presentinvention and, initially, to FIGURE 1 for this purpose, it will be seenthat the hot-metal production apparatus has been indicated in itsentirety by reference numeral and it includes a cupola furnace 12connected to both compartments 14 and 16 of a refining furnace 18 bymeans of a branched hot-metal transfer runners 20. The cupola furnaceitself is a standard item found in nearly every malleable iron foundry.Into it is charged a composition capable of producing a melt having acarhon-content in the range of between approximately 2.8 to 3.0 percent.Ordinarily, the capacity of a cupola furnace is entirely adequate tosatisfy the entire production requirements of the foundry. The moltenmetal from the cupola 12 is transferred to the refining furnace at atemperature of approximately 2780 F. by means of the runner 20 whichconsist usually of more or less trough-shaped pieces of refractorymaterial. In the usual installations, the entire output from the cupolafurnace is fed to a common single-compartment refining furnace whereadjustments are made to meet the required carbon range.

In accordance with the teaching of the instant invention, on the otherhand, branched runner 2b divides the output from the cupola furnace anddelivers same to separate compartments 14 and 16 of the refiningfurnace. Both compartments of the holding furnace are seldom, if ever,filled simultaneously and a simple, but effective, procedure that can beused to fill only one of the compartments is to erect a temporary muddam as indicated at 22 thus blocking of the branch 24 of the runnerleading to compartment 16 while, at the same time, allowing the moltenmetal to flow into compartment 14 through the other branch runner 26. Itshould, perhaps, be mentioned that automatic metering devices can alsobe employed in runner 20 in place of the mud darn 22 that will eliminatethe necessity for anyone attending the transfer of metal from the cupolato one of the refining furnace compartments; however, removable mud damsare entirely satisfactory for purposes of the present descriptionwithout becoming involved in more sophisticated apparatus that performsthis self-same function.

In the particular embodiment of the refining furnace 18 illustratedsomewhat schematically herein, it includes only two compartments 12 and14. It is to be understood, however, that the same principles to beoutlined presently are equally applicable to multi-compartmentedrefining furnaces having more than two hot-metal reservoirs.

Next, with reference to both figures of the drawing, high-carbon orcupola iron enters compartments 12 and 14 through ports 28 and 30 thatare located in the same horizontal plane and well above the furnacefloor 32. In addition to the floor, the furnace includes sidewalls 34and 36 as well as end walls 38 and 40, all of which are faced with arefractory lining. In addition, the top of the furnace is closed by acover 42. The most significant feature of the refining furnace, however,is the inclusion of partition wall 44 that is, likewise, formed ofrefractory material and constitutes the means by which the interior isdivided into separate hot-metal compartments. As illustrated, thispartition wall is located midway between the endwalls however, as apractical matter, it may be desirable to have one compartment largerthan the other depending on the requirements for a given grade of iron.Partition wall 44 is integrated into both sidewalls and the floor so asto form essentially fluid-tight compartments r the original high-carbonmelt.

with no access therebetween except over the top of the partition. It isquite important, that the liquids in the various compartments be sealedoff from one another While, at the same time, permitting both metalbaths to be treated simultaneously by flame sweeping across the surfacesthereof. Accordingly, it has proven quite satisfactory to maintain theliquid level in both compartments at the height of ports 28 and 30 thatlie well underneath the cover and have the partition wall extend abovethe surface of the baths approximately two inches. In this way, amplespace is provided between the underside of the cover and surface of thebaths substantially unobstructed by the partition to allow the freepassage of flame between compartments. The partition wall height abovethe liquid level as above stated also appears entirely adequate toeliminate cross contamination between baths.

The molten metal in both compartments of the refining furnace enters asaforesaid at about 2780 F., whereupon, a flame entering through nozzle46 in endwall 38 is directed across the surface of both baths to bringthe temperature on up to a range of between approximately 2830 to 2860F. Compartment 14 adjacent nozzle 46 is preferably used for theproduction of low and medium-carbon iron from the high carbon melt takenfrom the cupola. This is accomplished by adjusting the flame that issuesfrom nozzle 46 so as to insure a strong oxidizing environment. Then, byperiodically removing the slag from the surface of the metal bath incompartment 14 through slag removal door 48 in sidewall 36, thisparticular bath is exposed to the action of the oxidizing atmosphereproduced by the flame passing over the surface thereof. As a result, itis possible to effect a substantial reduction in the carbon content ofthe bath in compartment 14 thus producing in time either a medium or lowcarbon iron from For example, it can be shown that a charge of fifteentons of high-carbon iron in oxidizing compartment 14 will have thecarbon content thereof reduced at a rate of approximately 0.4% an hourand more if treated as outlined above.

Compartment 16 located farthest from nozzle 46, on the other hand, isutilized as the source of high carboniron having the same or nearly thesame composition as the original melt. In order to maintain thehighcarbon content of the bath in compartment 16 and prevent same frombeing acted upon by the oxidizing action of the flame passing over thesurface thereof, it is necessary that this high-carbon bath remaincovered at all times with a slag layer. The only exception to this iswhen minor reductions in carbon-content are necessary even in this bath,whereupon, the slag layer can be removed therefrom with paddles throughslag door 50 for the relatively brief .period necessary to accomplishthe desired adjustments. Note also that compartment 16 is provided witha hot-metal tap 52 by means of which carbon-rich metal can be ladledfrom the slag-covered bath and transferred to the other compartment viabranch runner 26 and port 28. Obviously, this procedure could bereversed to transfer carbon-lean hot metal to the highcarbon melt;however, this is seldom necessary and, therefore, no provision has beenshown for tapping metal from the bath in compartment 14 by means of aladle.

By maintaining the bath in compartment 16 covered at all times with aslag blanket, it becomes possible to perform a number of metallugicaloperations on the bath that is kept relatively free of slag in additionto reductions in carbon-content down to about 2.3 to 2.5 percent. Forexample, sufiicient carbon reduction to produce steels or semi-steelscan be accomplished by providing lancing jets 5 lentering through theside walls 34 and 36 or in that [portion of the cover 42 overlyingcompartment 14- as shown in FIGURE 2 by means of which additional oxygencan be introduced directly into the bath. Also, various types offerro-alloys, calcium carbide and other carbonaceous materials could beintroduced directly into the melt within compartment 14 withouteffecting the composition of the bath in the other compartment. It even'becomes possible to maintain close control over impurities such as isnecessary to produce high integrity iron and ferrous alloys. Secondaryslagging operations can be conducted and required in either of the twocompartments. Furthermore, the adjustment of other constituents of themelt besides carbon becomes possible. For instance, by introducing limein a nitrogen gas carrier, the sulfur-content can be controlled and anoxidizing sla-g step permits similar control over phosphorous.

The metal is drawn off to the casting lines through taps 56 and 58 thatconnect into compartments 14 and 16 respectively. Accordingly, it willbe seen that theabove-described hot-metal production facility forfoundries together with the method employed therewith comprise a noveland Worthwhile additions to the techniques and apparatus ordinarilyemployed in the manufacture of malleable iron castings and the like.While only a single embodiment of the invention has been disclosed, andit rather schematically, it is considered adequate to outline the novelprinciples involved. I realize, of course, that certain changes andmodifications may well occur to those skilled in the foundry art withinthe broad teaching hereof; hence, it is my intention that the scope ofprotection afforded hereby shall be limited only insofar as saidlimitations are expressly set forth in the appended claims.

What is claimed is:

1. Molten metal production apparatus for foundries and the like whichcomprises in combination: a cupola furnace adapted to receive a chargeof high-carbon iron and melt same; a refining furnace having at leasttwo refractory lined hot metal compartments separated from one anotherby a partition wall, a cover forming a closure for said compartments,said partition wall extending above the liquid level of the molten metalin adjacent compartments thus preventing intermixing thereof Whileallowing the free transfer of heat therebetween; rbranched runner meansinterconnecting the cupola furnace in series with each compartment ofthe refining furnace for the transfer of molten metal thereto, saidrunner means connecting each compartment of the refining furnace inparallel with one another; and, oxidizing flame jet means the refiningfurnace in position to direct a flame across the partition wall andsimultaneously raise the temperature of the molten metal in the twocompartments separated by said partition wall; and, means located in thecompartment containing the flame jet allowing for the removal of anyslag forming on the surface of the molten metal contained therein sothat said flame can sweep across the exposed surface of said slaglessmetal bath and oxidize same to effect a reduction in its carboncontentwithout substantially altering the composition of the slag-coveredmolten metal in the adjacent compartment.

2. The combination as set forth in claim 1 in which removabledam-forming means are selectely positioned in branches of the runnermeans capable of blocking the flow of the high-carbon melt from thecupola furnace into the particular refining furnace compartmentconnected to receive same from said blocked branch and redirecting saidmelt into the remaining runner branches and compartments connectedthereto.

3. The combination as set forth in claim 1 in which separate hot-metaltaps are provided in each compartment of the refining furnace so thatthe molten metal compositions contained therein can be separatelyutilized.

4. The combination as set forth in claim 1 in which conduit-formingmeans connectable to a source of oxygen and terminating beneath thesurface of the melt are provided in the compartment containing the flamejet for introducing oxygen directly into the molten metal containedtherein.

5. The refining furnace comprising, a refractory-lined vessel includinga floor, sidewalls and endwalls, a partition wall formed of a refractorymaterial dividing the interior of the vessel into two liquid-tightcompartments, a cover forming a closure for the vessel, said partitionwall terminating in spaced relation beneath the cover and cooperatingtherewith to define a gap therebetween adapted to permit the freecirculation of heat between compartments, a pair of horizontally-alignedinlets located in one of said outer walls of each compartment inposition spaced beneath the top edge of the partition wall for directintroduction of molten metal into each compartment, a flame jet locatedin one endwall of the vessel above the inlets in position to direct aflame across the top of the partition wall, access means located in oneof the outside walls of the compartment containing the jet positioned topermit removal of any slag forming on the surface of the molten metalcontained therein, and openable melt-removal taps positioned in anoutside wall of each compartment communicating the interior thereofbeneath the surface of the melt for Withdrawing the molten metal in saidcompartment.

6. The refining furnace as set forth in claim 5 in which the partitionwall extends approximately two inches above the level of the moltenmetal in the two compartments when filled to the inlets.

7. The refining furnace as set forth in claim 5 in which conduit-formingmeans connectable to a source of oxygen and terminating beneath thelevel of the melt are provided for introducing oxygen directly into themolten metal both contained in the compartment having the jet.

8. The refining furnace as set forth in claim 5 in which access meansare provided in an outside wall of the compartment remote from the jet,said access means communicating the interior of said remote compartmentbeneath the slag layer formed atop the melt thus providing for removalof the carbon-rich molten metal contained therein.

9. The refining furnace as set forth in claim 8 in which second accessmeans are provided in an outside wall of the compartment remote from thejet, said second access means being located to communicate the interiorthereof at the level of the slag layer therein for removal of slagforming on the surface of the metal in said remote compartment.

References Cited by the Examiner UNITED STATES PATENTS 475,609 5/ 1892Richords 266--33 702,526 6/ 1902 Ash 266-33 1,878,623 9/1932 Durbin"26611 2,794,631 6/1957 Becker et al. 26613 2,799,492 7/ 1957 Hobenreichet a1. 266-13 2,862,810 12/1958 Alexandrovsky 266--35 X 2,875,037 2/1959Wright -46 2,958,597 11/ 1960 Churcher 75-46 3,062,524 1l/ 1962 Leroy etal 266-34 WHITMORE A. WILTZ, Primary Examiner.

WINSTON A. DOUGLAS, MORRIS 0. WOLK,

Examiners.

5. THE REFINING FURNACE COMPRISING, A REFRACTORY-LINED VESSEL INCLUDINGA FLOOR, SIDEWALLS AND ENDWALLS, A PARTITION WALL FORMED OF A REFRACTORYMATERIAL DIVIDING THE INTERIOR OF THE VESSEL INTO TWO LIQUID-TIGHTCOMPARTMENTS, A COVER FORMING A CLOSURE FOR THE VESSEL, SAID PARTITIONWALL TERMINATING IN SPACED RELATION BENEATH THE COVER AND COOPERATINGTHEREWITH TO DEFINE A GAP THEREBETWEEN ADAPTED TO PERMIT THE FREECIRCULATION OF HEAT BETWEEN COMPARTMENTS, A PAIR OF HORIZONTALLY-ALIGNEDINLETS LOCATED IN ONE OF SAID OUTER WALLS OF EACH COMPARTMENT INPOSITION SPACED BENEATH THE TOP EDGE OF THE PARTITION WALL FOR DIRECTINTRODUCTION OF MOLTEN METAL INTO EACH COMPARTMENT, A FLAME JET LOCATEDIN ONE ENDWALL OF THE VESSEL ABOVE THE INLETS IN POSITION TO DIRECT AFLAME ACROSS THE TOP OF THE PARTITION WALL, ACCESS MEANS LOCATED IN ONEOF THE OUTSIDE WALLS OF THE COMPARTMENT CONTAINING THE JET POSITIONED TOPERMIT REMOVAL OF ANY SLAG FORMING ON THE SURFACE OF THE MOLTEN METALCONTAINED THEREIN, AND OPENABLE MELT-REMOVAL TAPS POSITIONED IN ANOUTSIDE WALL OF EACH COMPARTMENT COMMUNICATING THE INTERIOR THEREOFBENEATH THE SURFACE OF THE MELT FOR WITHDRAWING THE MOLTEN METAL IN SAIDCOMPARTMENT.